Log periodic rotating antenna

ABSTRACT

A ROTATABLE ANTENNA STRUCTURE INCLUDES A RADIATING ARRAY SUPPORTED IN A PLANE ABOVE A SUPPORT CONSTRUCTION COMPRISING BOOMS AND CABLES.

M. J. THOMAS 3,553,701

' Los PERIoDIc ROTATING ANTENNA Jan. 5, 1 971 Filed May 27,1 1968 7Sheets-sheet 1 m K LL v INVENTOR.

o o Maxime J; Thomas,

norneys M. J. THOMAS Los PERIoDIc ROTATING ANTENNA i 7 Sheets-Sheet zFiled May 27, 1968 M. J. THOMAS LOG f-ERIODIC ROTATING ANTENNA Jan. 57

' '7 Sheets-Sheet 3 Filed May 27, 196B INVENTOR Maxime J. Thomas BY 25%,QM M forneys Jan. 5, 1971 M. J. THOMAS l3,553,701

` I n LOG PERIODIO ROTATING ANTENNA Filed May 27,' y196e 7 Sheexsheet 4'Figs y HWENTORv Maxime J. Thomas f/4, 34M Si@ l ftor'heys Jan. 5, 1971j pM. .1; THOMAS 3,553,701

LOG PERIODIC ROTATING ANTENNA Filed May 27, 1968 Sheets-Sheet' 5INVENTOR.

7 Sheets-Sheet 6 INVENTOL Jan. 5,1971 M.` J. THoMAs LOG PERIODICROTATING ANTENNA Filed May 27. 196B Jan. 5,1971V M. J. THOMAS LOGPERIODIC `ROTATING ANTENNA Filed may 27,1968

7 Sheets-Sheet '7 ,1 S RSM v, a. e mma/Mm No l o van n N A e .m XM a M YB Unted States Patent O U.S. Cl. 343-766 4 Claims ABSTRACT OF THEDISCLOSURE A rotatable antenna structure includes a radiating arraysupported in a plane above a support construction comprising booms andcables.

BACKGROUND OF THE INVENTION This invention pertains to an antenna systemsupport structure, particularly useful as a rotating log periodicantenna.

Log periodic antennas are generally characterized by a number ofsubstantially parallel dipole radiating elements each respectivelyhaving a length, and being disposed at spacings, dened by a givenrelationship from one to the next. Characteristically, these radiatingelements have consisted of long, hollow, tubular members which arecantilevered to extend out from a common spine or support boom. Thus,such an array becomes quite ponderous as the radiating elements becomelonger and longer.

Heretofore, antenna systems, and particularly rotating antenna systems,have been handicapped by their structural configurations whereby theirweight, bulk, and awkwardness serve to handicap their employment. Indirectional antenna systems to be rotated to a desired azimuth, theradiating array structure should be as little subject to weatherconditions, such as icing, high winds, or both, whereby it can remaindirectionally oriented without undue strain on the structure.

Inasmuch as the spacing between the dipole radiating elements will bedictated by the radiating array, in many instances, such as where thespacing is a logarithmic function, the spacing between each adjacentpair of elements will not be the same as between other adjacent pairs ofradiating elements. Further, it is necessary, for electrical reasons, toensure that structure adjacent to the radiating elements be placed clearof adjacent support structure so as not to create undue interferencewith such structure.

In the past this requirement has necessitated additional expense in thefabrication of the support boom structures.

SUMMARY OF THE INVENTION AND OBJECTS According to the present invention,the array supporting structure serves to space the radiating array abovethe plane of the support boorn structure so as to minimize certain ofthe foregoing and other problems heretofore experienced and to permit asimpliiied boom construction to be utilized.

In addition, according to the invention, the array supporting systemserves to permit a substantial reduction in the projected area of thebooms so as to minimize the eiiects of wind. The radiating arrayparticipates as a part of the support system to ease the load otherwiseacting upon the lcantilevered outer ends of the booms whereby the bulkand mass of the booms may be reduced.

Accordingly, it is a general object of the invention to provide animproved antenna system.

Another object of the invention is to provide an improved antenna systemcharacterized by a radiating array supported above the plane of thesupport booms so as to minimize electrical and mechanical interferencetherebetween, and organized in a manner serving to ac- 3,553,701Patented Jan. 5, 1971 ICC complish the above and other objects as willbecome more clearly apparent from the following description, consideredin conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a perspective view showingthe upper portion of a support tower and radiating array supportedaccording to the invention.

FIGS. 2 and 3 are respectively enlarged detailed sections taken alongthe lines 2-2 and 3-3 of FIG. 1.

FIG. 4 is a side elevation View of the structure shown in FIG. 1.

FIG. 5 is an enlarged detailed perspective view showing the portiondesignated by lthe line 5 5 of FIG. 4.

FIG. 6 is an enlarged detailed View taken along the line 6-6 of FIG. 4.

FIG. 7 is an enlarged vside elevation view taken in the zone bounded bythe line 7-7 of FIG. 4.

FIG. 8 is a plan view of FIG. 4 viewed from above.

FIG. 9 is an enlarged detailed view in the zone bounded by the line 9 9of FIG. 8.

FIG. 10 shows an enlarged plan view, viewed from above, taken along theline 10-10' of FIG. 7.

FIG. ll is an enlarged perspective View of the detail as shown in theregion bounded by line 11-11 of FIG. 1.

FIG. 12 is an enlarged perspective view showing the detail forconnection being made: between radiator elements and feed lines.

FIG. 13 is an enlarged detailed perspective view showing the manner ofspacing feed lines from the boom structure and from support bridles asshown in the region 13-13 of FIG. 4.

FIG. 14 is a plan view of a portion of one of the support booms.

FIG. 15 is an enlarged detailed view of the portion bounded by line15-15 of FIG. 14.

FIG. 16` is a transverse section view taken along the line 16-1'6 ofFIG. 15.

FIG. 17 shows a diagram for explanation of forces acting upon a supportboom structure, according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In general, as will be describedin more detail further below, there has been provided an antenna systemto be carried atop a support tower and which is provided with aradiating array configuration of spaced iiexible radiating elements. Thearray supporting construction is characterized as having a peripheryconfiguration on the order of but not substantially greater'than theperiphery of the array configuration, and the array supportingconstruction serves to support the plan of the radiating array in aspaced relation above the support structure.

Thus, each of the booms is inclined upwardly so that the appliedcompressive forces from the load of the array are directedlongitudinally along each boom toward a common axis of rotation. Theload of the array also applies an upwardly acting component or moment offorce to the cantilevered unsupported outer ends of the booms so as tocounteract the bending stresses which are otherwise acting downwardlyupon these portions of the booms. In this manner, bending stresses inthe booms are relieved.

It is within the further contemplation of the invention herein that thethree longitudinally extending boom-forming elements are characterizedby triangular cross-section defined by a plurality of boom-formingelements. The booms are oriented whereby the base of the triangularcross-section appears at the top olf the boom, while the apex of thetriangular cross-section is disposed at the bottom of the boom. In thismanner, greater strength of boom structure is obtained and the bulk ofthe boom may be reduced so as to aid in minimizing the effects of windacting upon the antenna system.

Referring in greater detail to the construction, there is shown in FIG.l an antenna system including generally a support tower assembly 11,including the usual guy wires 1'2 secured thereto, and a rotatablydisposed antenna assembly 13. Antenna assembly 13 comprises both theradiating array 14 and the array supporting assembly 16.

In general, aS will be understood by those skilled in antenna systems,the radiating elements 17 function as dipoles fed by feed lines 18 whichare, in turn, electrically coupled to return lines 19 returning alongthe central boom 21 and ultimately downwardly along the axis of rotationof antenna assembly 13 to a balun (not shown).

In an antenna system of the type described, it is important that thesupport structure not interfere, either electrically or mechanically,with the radiating array while holding the array in transmittingposition.

Accordingly, each of three support booms 21, 22, 23 has lbeen angledslightly upwardly at an angle, on the order of 1.4 to the horizontal andfrom booms 21-23 array 1-4 is supported out of the plane of the booms asnow to be described.

Atop support tower 11 means have been provided to collect and supportthe root portions of each of the three booms 21-23 in a rotatablemounting arrangement where- 'by the overturning moment to be experiencedby the mounting bearing assembly has been minimized for irnprovedfunctioning of the bearing and rotatable drive, and for the additionaladvantage of foreshortening support tower 11.

Thus, as best shown in FIGS. 7 and 10, at the top of the main portion ofsupport tower 11, a bearing assembly 24 supports a mounting cage 26 forreceiving and supporting the root portion of each of booms 21-23.

As arranged herein, these root portions of booms 21-23 are carriedsubstantially contiguous to the bearing assembly 24 whereby theoverturning moment experienced by bearing assembly 24 will be minimal.Bearing assembly 24 includes Ibase plate 27 secured to the upper ends ofa number of cross braces 28. Base plate 27 carries the stationary race29 of a ball bearing assembly which further includes a rotatable race31. Race 31 is subdivided into a relatively smooth upper portion and alower portion which has `been provided with drive teeth 32 which serveto engage the pinion 33 of a drive motor 34. As thus arranged, motor 34can readily rotate the outer race 31 with respect to stationary race 29and, by means now to be described, rotate the array supporting assembly16 (FIG. 1).

Thus, the two portions of rotatable race 31 are joined by means of bolts36 which serve to clamp a mounting ring 37 tightly to an annularprotective skirt 38 which covers, and protects from the elements, theentire bearing assembly 24.

Mounting ring 37, in turn, supports three lower rail stubs 39 of across-section configuration adapted to receive and lbe bolted to thelower rails 41 of each of booms 21-23. In addition, mounting ring 37carries the cage-like support structure consisting of cross braces 42which are joined at their upper ends in mutual support to atrian-gularly shaped frame 43, each element of which is of a boxconstruction or square tube construction to provide considerablestrength thereto. Frame 43 carries upper rail stubs 44 secured thereto,as by welding, for example, which serve to receive the two upper rails46 of each of booms 21423. Accordingly, it will be readily apparent thateach boom 21-23 includes three longitudinally extending boom-formingelements, such as the rails 41, 46, arranged to provide a triangularcross-section disposed in a manner to orient the base of the triangle atthe top of the boom and the apex at the bottom so as to increase thestrength of each boom without increasing the mass or size of same. Rails41, 46 are spaced apart by means of the boom braces 47 uniformly angledback and forth between the rails along the length of each boom 21-23.Thus, the manufacture of the booms can be accomplished in conventionalstyle, and lby virtue of elevating the radiating array above the arraysupporting booms, the manufacture of these booms 21-23 can beaccomplished without consideration as to whether or not the radiatingelements 17 may be mechanically or electrically interfered with by thestructure of the boom due to the fact that the spacing between elements17 is based upon a logarithmic relationship, whereas the spacing betweenboom braces -47 is maintained at a uniform constant relationship.

In copending application Ser. No. 648,475 of William I.. Werner for aLog Periodic Rotating Antenna, which is assigned to the assignee herein,a rotatable log periodic antenna array has been disclosed wherein theradiating elements each comprise a pair of wire portions to be supportedat their outer ends to ydiverge at a relatively narrow angle from eachother. The radiating elements are supported by a cable coupled tosupport each of the wire portions. The main supporting cable is disposedbetween the ends of the radiating elements to provide the major supportfor the radiating elements. The outer ends of the radiating elements areadditionally supported variously by another cable or other means asdisclosed therein.

By means now to be described, the entire load of the radiating elementscan Lbe supported from their tip ends by a single cable 48.

Thus, each of booms 21-23 angles slightly upwardly relative to thehorizontal and extends radially outwardly from the axis of rotation ofarray 14. For example, as noted in FIG. 7, the upwardly divergent angleis indicated by phantom lines as at reference numeral 49 as being on theorder of 1.4". Radiation array 14 consists of the transversely extendingradiating elements 17. Each radiating element 17 (FIG. 9) consists of apair of wire portions 51 held at the tip end 52 of element 17 by anassembly 53 of suitable insulative material pivotally mounted in aconventional device 54 attached to dielectric cable 48.

The inner ends of radiating elements 17 are coupled (FIG. l2) to feedlines 18 by means of spreader insulative bars 56 which serve to spreadand properly separate and evenly tension the inner ends of wire portions51. Bars 56 are pivotally supported on the opposite ends of a joiner bar57, of insulative material, whereby the entire dipole radiating element17 has been formed.

Feed lines 18 are supported equi-distant from the inner ends of wireportions 51 by means of the feed jumper bars 58 which carry a swagedfitting 59 at their outer ends to make contact with the feed lines 18.

By disposing feed lines 18 in spaced relation above and along boom 21,it will be apparent that the foregoing connections made with feed lines18 by radiating elements 17 can be made without regard to the spacingand construction of interfering parts of boom 21. Accordingly, at theouter end of feed lines 18 (FIG. 5), each line 18 is coupled by means ofa swaged tting 61 to a tension equalizing assembly 62. Assembly `62,consists of the pair of insulative bars 63 pivotally coupled to straps64 at one end and to a support yoke 66 at the other. An eyebolt l67anchors yoke 66 from an upwardly extending extension `68 of rigid,rectangular cross-section whereby the outer supported end of lines 18terminates in modest spaced relation above boom 21.

Feed lines 18 are held in substantially constant spaced relation withrespect to boom 21 along its length by means of a clamping assembly 69comprised of a pair of crossed I shaped braces 71 pivotally supported attheir opposite ends respectively to upper rails 46 and to an insulatormember 72 which serves to dispose one of feed lines 18 centrally of alarge opening 73 therethrough as by means of the stand-off insulators74, 76 swaged onto feed lines 18.

Feed lines 18 extend from the outer tip of boom 21 as shown in FIG. 5rearwardly of the radiating array 14 along boom 21, as supported by theapparatus shown in FIG. 13, to the axis of rotation of array 14 andcontinues on rearwardly to be electrically coupled to radiating elements17 located between booms 22, 23. Means are provided for tensioning thatportion of feed lines 18 extending forwardly from the axis of rotationof array 14- in a manner independent of the means for tensioning feedlines 18 in the rear portion thereof. Thus, feed lines 18 may beconsidered as having been mechanically divided into a major portionextending forwardly of the axis of rotation of array 14 and a minorportion extending rearwardly from the axis of rotation.

The major and minor portions of feed lines 18 are independentlytensioned by attachment to means located at the axis of rotation ofarray 14 and are electrically connected by means of the jumper lines(FIG. 7) 77. Thus, the ends of lines 18 for the major portion thereofare secured to a support tower extension, or mast 78 comprised of a trioof upwardly extending rails 79 mounted in vertically disposed rail stubs81. Insulators 82, pivotally secured at each end, engage and hold a loop83 of each feed line 18 as formed by doubling a portion of the feed lineback upon itself and employing a swage fitting 84 to form the loop 83. Ajumper line 77 is also swaged, by as the fitting 86, onto feed line 18so as to provide electrical coupling with the rear or minor portion offeed lines 18. p

Tensioning of the latter is similarly accomplished and accordingly neednot be described in further detail, other than to note the pair ofstabilizer plate 87 anchored by the eyebolt 88 secured to one of rails79. Jumper lines 77 are held clear of rails 79 by means of stand-offinsulators 89.

Means serving to couple the rear end of feed lines 18 is best shown inFIG. 11 and consists of a tension equalizer assembly 91 comparable tothe equalizer assembly 62 as previously described. Laterally extendingwire portions 51 of the rearmost radiation element 17 are held by meansof the rhombus-shaped insulator plate 92 as described earlier aboverelative to insulator 72 in FIG. 13. In the present instance, however,electrical coupling to wire portions 51 from feed lines 18 has been madeby utilizing jumper wires 93.

Rearwardly of the tension equalizer assembly 91 attachment is made to apair of parasitic radiator elements 94. Thus, spacer 96 ofnon-insulative material is clamped thereto and a longitudinal tug isthereby applied to feed lines 18 by bridling, or slightly angling theparasitic elements 94 rearwardly (FIG. 8). The longitudinal tug 100(FIG. 11) need not be too great inasmuch as only the minor portion ofthe overall feed lines is required to be tensioned in this manner.

Accordingly, it is readily apparent that the rearmost radiator element,such as parasitic elements 94, have been coupled to the end of the minorportion of feed lines 18 for tensioning the minor portion of the feedlines while the major portion of feed lines 18 is tensioned byadjustment of the adjustable eyebolt 67 (FIG. 5). Tensioning of each ofthe two portions is essentially independent of the other whereby only alimited strain is applied to the tensioning radiator elements at therear of array 14.

As in other log periodic antennas, return lines have been provided.Referring to FIG. 5, four return lines 19 are disposed and evenlytensioned by the dual tension equalizing assemblies 98, 99 mutuallydisposed at right angles to each other and adjusted in tension by meansof r the elongated eyebolt 101. Each assembly 98, 99 is comparable tothose shown relative to the tension equalizer assembly 62 and need notbe further described.

Means serving to maintain generally uniform spacing between return lines19 along boom 21 comprises a num- 6 ber of devices as shown in FIG. 2`disposed at intervals along boom 21. Thus, each of these devicescomprises in general an H shaped central supporting unit mounted forslight pivotal adjusting movements along the geometric center of thetriangular cross-section of boom 21.

More particularly, an insulated spacer bar 103 supports each of twopairs of aluminum clamps 102, each of which has been formed withpassages for engaging the return lines 19. Spacer bar 103 has beenpivotally mounted at its ends respectively to a T-shaped metallicextension 104 and a metallic link 106. The extension T 104 and link 106are, in turn, respectively coupled to insulators 107 which are eachrespectively engaged by adjustable mountings 109. In this manner, itwill be apparent that return lines 19 will be carried centrally alongboom 21 rearwardly toward the axis of rotation of array 14. Uponreaching the axis of rotation of array 14, return lines 19 changedirection and pass downwardly of the main support tower 11.

Referring to FIGS. 7 and 10, means have been shown for making thistransition and for suitably tensioning each of the two portions ofreturn lines 19, i.e., the horizontal portion and the vertical portion.Thus, the four horizontal return lines 19 and four vertical return lineportions 97 are. each coupled (FIG. 7) to spreader bars 111. Each bar111` serves to space the ends of its associated pair of return lines 19,97 and the two bars 111 are each connected by a round rod 112 bent at a90 angle and secured at its opposite ends respectively to each of thetwo bars 111. Rod 112 is, in turn, held under tension by means of theadjustable tension equalizing assembly 113.

Assembly 113 comprises two pairs of shackle links 114, each pair ofwhich is coupled to a shackle 116 carried on the end of a pair ofinsulators 117 pivotally coupled, in turn, to stabilizer bars 118 heldunder adjustable tension by means of the eyebolt 119. Eye bolt 119threadedly engages the transversely extending inverted angle mountingbar 121.

As thus arranged, it is apparent that return lines 19 make thetransition from horizontal to vertical and extend downwardly as returnline portions 97 centrally of the main support tower assembly 11 where,at their lower end, they ultimately reach a balun of conventional design(not shown).

Inasmuch as the radiating array 14 rotates relative to the stationarysupport tower assembly 11, in the manner described and shown in theabove identified patent application, the vertically extending returnline portions 97 will twist as a group. Accordingly, means are providedwhereby the spacing remains constant between each of the return lines 97during such twisting movement.

The twisting movement may occur roughly in the upper 25 feet of supporttower assembly 11, whereas the remaining lower extent of the downwardlyextending return lines 97 may be held stationary and substantially freeof any twisting. The lower portion is mounted by the means shown in FIG.3 centrally of support tower 11, whereas the upper portion of returnlines 97 is carried by a portion of the structure shown in FIG. 3 but inan unanchored manner.

Thus, as described relative to the devices shown in FIG. 2, FIG. 3similarly provides an H shaped spacer construction 122 constructed inthe manner described relative to comparable components shown in FIG. 2.In the upper extent of tower assembly 11 the spacer construction 122stands by itself supported merely by the downwardly extending returnlines 97. The lower portions of the return lines 97 are firmly supportedagainst twisting by the remainder of the apparatus shown in FIG. 3 whichis comparable to that apparatus shown in FIG. 2 and need not be furtherdescribed herein.

Finally, each of the two-rearwardly-directed booms 22, 23 iselectrically subdivided into discrete insulated sections by theinsulative splice as shown in FIGS. 1446. Each splice 123 comprisesmetallic adaptors 124 formed at one end with a cylindrically shapedsocket 126 or cup for receiving a solid cylindrically shaped bridgingmember 127 of rigid insulative material, and at is other end with achanneled stub rail 128 adapted to be bolted, as shown in FIG. 16, tothe rail portions of a type forming booms 22, 23.

As is known, any time an elongated boom is supported in a cantileveredfashion from its end, the outer unsupported end of the boom is subjectto considerable downward bending forces imposing severe stress on theboom structure as well as upon its mounting. Each of booms 21-23 isguyed from above, as shown in FIGS. l, 4 and 8, by support cables 129,131, 132, respectively, extending from the upper end of support towerextension 78 to a bridle 133 (FIG. 13). Cables 131 and 132 are, as shownin FIG. 4, subdivided by means of electrical insulators 134.

The outer unguyed end portion of each boom will normally experiencedownwardly acting bending stresses caused by the unsupported weight ofsuch boom portions. The radiating array herein contributes counteractingforces forming an eccentric upwardly acting moment serving to relievesuch bending stresses. Thus, referring to the diagram shown in FIG. 17,the supporting action derived from the array itself may be more clearlyunderstood.

The unsupported cantilevered outer end portions, such as 145 in FIG. 17,including the Outrigger 140 and array elements, tends t bend downwardlyabout a bending point 146 located along the centroid 147 of boorn 145and immediately beneath the point of support 148 supplied by the guyingcable 129. Catenary support cables 48 (shown in FIG. l7 as a singlecable 48 for diagrammatic purposes and clarity) when loaded byenvironmental forces imposed upon the array elements develop a force, f,acting mainly along the boom 21 toward the center of rotation of thearray, but disposed above the centroid 147 of the boom so as to definean eccentric moment arm, L1, to develop a counteracting moment t0 thatmoment developed by the weight, Fg, of the boom portion 1-45 and thearray portion acting about point 146. Thus, the counteracting momentacts upwardly substantially normal to the centroid axis 147.

Stresses effected by the arrays eccentric location with respect to thetilted booms are not restricted to point 146 alone. These stressestravel throughout the boom and their effect ends at the junction whereall three booms come together.

Thus, by supporting the array above the booms, the array tends tocontribute to its own support and it becomes possible to construct aboom of lighter weight material and of lower mass with a lower profileexposed to the wind.

vBooms 21-23 are guyed from below by means of cables 136, 137 and 138(FIG. 1) by means of the downwardly and outwardly diverging struts 139which are also guyed in a triangular disposition by means of the cables141.

It will be apparent that the arrangement of struts 139 and guying cables136-138 and 141 are disposed beneath the level of bearing assembly 24whereby booms 21-23 have been securely stabilized and advantageouslysupported while foreshortening the overall extent of support towerassembly 11.

From the foregoing, it will be readily evident that there has beenprovided an improved antenna construction providing a number ofsignificant advantages, such as the provision of an arrangement wherebythe boom construction may be of lesser mass and prole relieving criticalrequirements of material and construction which become quitesignificant, for example, where an antenna of the type described must belocated in a remote geographical region and operated over long periodsof time essentially without maintenance, observation or inspection.

It is further apparent the construction of each of booms 21-23 may beconventionally carried out without regard to any particular spacing ofthe radiating array elements 17. The manner of supporting the antennafor rotation serves to minimize the overturning moment which wouldotherwise act upon and impose severe requirements upon the bearingassembly located at the top of the support tower. Further, it Iwill beappreciated that the radiating elements are supported at their endssolely by a single cable inasmuch as the load requirements applied tosuch cable have been significantly relieved by virtue of the arrangementshown. Thus, a single cable at the ends of each of the radiatingelements becomes suflicient support and the array supportingconstruction is thereby provided with a periphery configuration on theorder of but not substantially greater than the periphery of theradiating array configuration itself. As mentioned, this position of theradiating array to lie in a plane above the array supportingconstruction has served to minimize the expense involved in theconstruction of booms for supporting such arrays.

Further, by disposing the two rails of each boom at the top of the boomand the third rail, forming the apex of the triangular cross-section,beneath the boom, greater strength is achieved in each boom for thematerial used and enhances the advantages of less boom profile and lessmassive structure is attained. Finally, the manner of independentlytensioning portions of the feed lines serves to permit less structure tobe employed in tensioning the minor or rear portion of the feed lines 19simply by attachment to parasitic elements such as the parasiticelements 94.

I claim:

1. In an antenna system the combination comprising a plurality of atleast three booms adapted to support an array of radiating elements, amain support tower portion, a bearing assembly disposed atop said towerportion having stationary and rotatable races, a motor at the upper endof said tower portion for driving said rotatable race, mounting meanssubstantially contiguous to said bearing assembly for receiving andsupporting the root portion of each of said booms, said booms extendingradially away from said tower portion, a support tower extension portioncarried by said mounting means, tensioned guying cables extendingbetween the tower extension portion and intermediate portions of thebooms, catenary cables extending between the ends of the booms, an arrayof radiating elements supported by said catenary cables above the booms,and support elements carried by the booms and supporting the catenarycables and array in a disposition causing the array to apply supportingforces to portions of each boom counter to forces tending to bend saidboom portions downwardly.

2. In an antenna system according to claim 1 further includingelectrical feed lines operably coupled to transversely extendingradiator elements and disposed in spaced relation along and above one ofsaid booms, a parasitic radiator element extending between two of thebooms, means carried by said tower extension portion serving toindependently support and tension major and minor portions of said feedlines, and means coupled between said minor portion and said parasiticelement to tension said minor portion of the feed lines.

3. In an antenna system to be carried atop a support tower, apparatuscomprising a radiating array of spaced exible wire radiating elements,and a plurality of at least three support booms radiating from a commonupright axis at their inner ends, cables means extending between theouter ends of the booms and placing the booms in compression at theirinner ends and supporting the array, means supporting the booms from aposition intermediate their respective ends to dispose the booms at aslightly upwardly inclined angle for carrying the array above the booms,support elements coupled to the ends of the booms and extending upwardlyto positions above the longitudinal axis of each boom, said cable meansbeing coupled to said support elements at said positions in tension toform an eccentric moment in each boom acting upwardly for counteringbending stresses in the booms otherwise acting downwardly upon portionsof said booms thereby relieving said boom portions from such stresses.

4. In an antenna system the combination comprising a plurality of atleast three booms adapted to support an array of radiating elements, amain support tower p0rtion, a bearing assembly disposed atop said towerportion having stationary and rotatable races, a motor at the upper endof said tower portion for driving said rotatable race, mounting meanssubstantially contiguous to said bearing assembly for receiving andsupporting the root portion of each of said booms, said booms extendingradially away from said tower portion, a support tower extension portioncarried by said mounting means, tensioned guying cables extendingbetween the tower extension portion and intermediate portions of thebooms, 20

an array of radiating elements supported by said booms above the booms,and in a disposition serving to apply supporting forces to portions ofeach boom counter to forces tending to bend said boom portionsdownwardly,

electrical feed lines operably coupled to transversely extendingradiator elements and disposed in spaced relation along and above one ofsaid. booms, a parasitic radiator element extending between two of thebooms, means carried by said tower extension portion serving toindependently support major and minor portions of said feed lines, andmeans coupled between said minor portion and said parasitic element totension said minor portion of the feed lines.

References Cited UNITED STATES PATENTS 2,145,024 1/ 1939 Bruce 343-882X2,583,747 1*/ 1952 Potter 343--890X 3,276,027 9/1966 Bell et al.343-7925 3,373,434 3/1968 Lorenzo et al 343-88IX 3,393,480 7/1968Groseclose et al. 343-882X ELI LIEBERMAN, Primary Examiner T. VEZEAU,Assistant Examiner Us. c1. X.R. 343*792.5, S14, 886, 89o

